FROM MINERAL TO ROCK MINERALS ALL AROUND US Minerals are all around us. They are used to make many of the products we use everyday. Minerals provide us with the metals that help us make cars, aircraft, jewelry and coins. Below is a list of other items we use that are made of minerals: lead pencils (graphite) Minerals are made of atoms (tiny particles) from fertilizer (potassium, sodium, calcium) different elements such as oxygen, carbon, lead and silicon. The atoms form simple patterns that give chalk (gypsum) mineral cystals characteristic shapes. The hidden flashbulb (zirconium) pattern of the packed together atoms is always the same in any particular mineral. Minerals can be identified by window glass/mirrors (silica) their color, density, hardness and shape. table salt (halite) Color: Streak is a mineral's color in powder form. It can be seen when the mineral is scraped across a Minerals that concentrate into deposits from which one tile. or more minerals and rocks may be extracted are called ores. In Michigan, iron ore (hematite) is mined in the Density: This is the mineral's weight per unit Upper Peninsula. The earliest commercial deposits volume. Water is assigned a density of 1 and the were found in Marquette County in 1844. Until about specific density measurements of other materials are 1900, Michigan was the leading producer of iron ore in compared to it. A mineral fragment that weighs 2.1 the United States. times as much as an equal volume of water has a density measurement of 2.1. Another mineral that brought attention to Michigan was the “native copper” deposits of the Keweenaw Peninsula Hardness: A mineral's hardness is one of the most in the western Upper Peninsula. This region became useful identification tools. The hardness scale looks world famous when Michigan was the leading producer like this: of copper in the U.S. between 1847-1887. This deposit is unique because the copper is not combined with other elements. THE BUILDING BLOCKS OF ROCK Minerals are the building blocks of rocks. Nature Shape: A mineral's shape (also called “habit”) can cements combinations of minerals together to form be a useful clue to a mineral's identity. Each shape rocks. Rocks are catagorized in three general groups has a specific name. For example, copper is according to the way they were formed. These groups dendritic. It is made up of thousands of tiny crystals are: forming a branching growth. Salt forms cube- IGNEOUS ROCKS: Igneous rocks are not all one kind, shaped crystals and quartz forms six-sided crystals. so they are put into two sub-groups according to the Cleavage: This is the surface along which a mineral manner and place in the earth where they were formed. has the tendancy to break. The number of cleavage Intrusive igneous rocks were formed by molten planes and the angles between them can provide rock, called magma, forced from the earth's interior useful clues to identification of minerals. into a cooling part of the earth's crust. As they Luster: Luster is the gloss of a mineral's surface. It cooled, their minerals formed large crystals. To is determined by the way light is reflected from a summarize, intrusive rocks are those that were mineral. pushed into other rocks. Extrusive igneous rocks are formed when magma is forced to the earth's surface as a result of volcanic activity. From Mineral to Rock – Page 1 of 2 SEDIMENTARY ROCKS: Sedimentary rocks are formed when loose sediment accumulates in layers that become cemented together. Sediment is material that comes from the wearing away of rocks caused by weathering affects. Two types of weathering affects create sediments. Mechanical weathering breaks down rocks into particles without changing the identities of the minerals in the rock. Ice is an important agent of mechanical weathering. Water seeps into the cracks and pore spaces of the rock. It expands when it freezes, forcing the cracks to widen. This results in pieces of rock being broken off. Heating and cooling of rock also contributes to mechanical weathering. Chemical weathering is the wearing away of rock by chemical reaction. In this process a rock's minerals are divided into finer particles that can be easily carried by the wind. Air and water are involved in many chemical reactions. Wind, water and ice transport weathered sediment. These agents of transportation reduce the size of the sediment particles and deposit them in new locations. Common sediments include mud, gravel, sand and silt. Sedimentary rocks can be classified into three groups. Clastic sedimentary rock is made of transported fragments from pre-existing rock. Examples of this type of rock are sandstone and shale. Carbonate sedimentary rock is abundant in Michigan. Limestone is an example of this type of sedimentary rock. Evaporite sedimentary rock is formed by the evaporation of salt water. Two examples of this type of rock are salt and gypsum. METAMORPHIC ROCKS: Metamorphic rocks are rocks that have gone through a chemical, mineral or structural alteration due to a change in their surroundings. The change usually takes place deep within the earth and is caused by high temperature and pressure. Examples of this type of rock include slate that was once shale and marble that was once limestone or dolomite. ROCK HUNT Ask each of the children in your group to find an unusual rock. This can be done at home in their backyards, at recess in the playground or on a family vacation or weekend outing. Ask them to complete the “Rock Hunt Report” worksheet. From Mineral to Rock – Page 2 of 2 .